In a sweeping cultural shift, comparable perhaps to Americans' quickening support of same-sex marriage, a majority of Americans now favor legalizing marijuana use, according to a Gallup poll released Tuesday. The survey showed that 58% of 1,028 respondents supported legalization, with 39% against.

That's a drop for the naysayers from just three years ago, when 50% of respondents opposed legalization -- a number already riding a long plummet from a high of 73% in the 1990s.

Gallup credited much of the surge to political independents, whose support for legalization jumped from 50% to 62% in less than a year.

And what a year it has been for marijuana advocates: Last November, voters in Colorado and Washington easily passed ballot initiatives -- 55% to 45% in each state -- to legalize the possession and sale of marijuana. In Colorado, the legalization measure got more votes than President Obama, who won the state.

After the victory, advocates and politicians alike were unsure how federal law-enforcement authorities would react to state laws that contradict federal laws that prohibit marijuana use and list it as a controlled substance.

Those tensions eased after the Justice Departmentannounced in August that federal officials would not interfere with voter-approved laws that legalized recreational marijuana use, as long as the state laws were strictly regulated.

In August, 38% of Gallup respondents said they'd tried marijuana. That's the highest number ever recorded by a Gallup survey, and yet it's only an incremental increase for a figure that has remained in the mid-30s since the 1980s.

Americans older than 65 remain the only age group that opposes marijuana legalization, with 53% against. Support grows stronger with each younger generation, with 18-to-29-year-olds supporting legalization 67% to 31%.